Dual-technology wireless networks are becoming more prevalent as operators begin deploying 4G wireless broadband networks, such as LTE and WiMAX, in conjunction with their existing 2G and 3G networks which include GSM, cdma2000, HRPD, UMTS, etc. These dual-technology networks may be deployed in the form of 4G networks side by side with 2G/3G networks to extend the wireless operators' network coverage, as overlaying 4G networks over existing 2G/3G networks to add capacity in specific areas, or a combination of both. Some examples of dual-technology networks include LTE-HRPD, WiMAX-HRPD networks, WiMAX-GERAN/UTRAN networks, 3GPP2, WiMAX-WiFi networks, and others. They may also include dual-technology 4G networks such as joint WiMAX-LTE access networks.
In order to take advantage of the extended network coverage and network capacity dual technology networks offer, dual-technology mode/multi-technology mode mobile devices (MS) capable of supporting multiple air interface technologies are required. As dual-technology wireless networks are deployed, wireless network operators are looking for ways to provide session continuity to customers across their dual technology networks as is currently available with the single technology network using handovers. This requires inter-technology handover support in the multi-mode MS and the heterogeneous joint access networks. An inter-technology handover may become necessary due to deteriorating radio conditions at the serving technology network, load balancing between the heterogeneous networks, temporary service outage at the serving network, operator policy for dual mode MSs, user preference for service in one technology network vs. another e.g. due to higher bandwidth, lower cost, or other reasons.
A packet session supported by a serving network may be comprised of one or more ‘service flows’ or ‘service instances’ supporting one or more packet type services. These may include, for example, Quality of Service (QoS) sensitive applications such as video streaming, gaming, voice over IP (VoIP) and other real time services where latency delays cannot be tolerated, and applications such as email, web browsing, or instant messaging with low QoS requirements where latency delays can be tolerated with little impact to the user experience. Session continuity refers to the ability to maintain an existing packet data session during handover from a serving base station, access point or network node to a target base station, access point or network node that used different wireless access technology. In order to maintain session continuity of existing packet data sessions during user mobility, a user's packet session must be handed over from a current serving node to a target node. In the case of inter-technology handovers, the serving and target nodes involved in the handoff support two different air interface technologies or radio access types (RAT) and network standards or technologies. Hence, prior to the handover, a new session must first be setup and packet session established at the target network.
Call setup, initial network entry or session registration in a wireless network includes authentication, authorization, and packet session registration procedures between the mobile device and the network. Handover in homogenous technology networks use standardized handover signaling protocols to optimize moving a mobile device's packet session from a source or serving node to a target node. Because inter-technology handover signaling protocols are not specified, inter-technology handovers, i.e. handing over a packet data session from a serving technology network to a heterogeneous target technology network, require initial network entry procedures to be completed on the target network first before the packet session active between the mobile device and the serving node can be handed off to the second heterogeneous technology node.
Completion of initial network entry procedures at a target technology node at the time of inter-technology handover is time consuming and results in unacceptable latency delays and potential packet loss during the inter-technology handover. Depending on the air interface technology supported by the mobile device and target technology network, completion of initial network entry procedures can take several seconds to achieve. These delays are unacceptable when handing off a packet data session comprised of QoS sensitive real time services.
In order to minimize latency delays during inter-technology handover, a multi-technology mode mobile device in a dual or multi technology coverage area may initiate network entry procedures at a target technology network prior to inter-technology handover is actually required while continuing to receive packet data service from the serving technology network. A multi mode MS continues receiving packet data service via the serving network while communicating with the target technology network via air interface signaling native to the target technology network to complete initial network entry procedures and establish a new packet session. Hence, a packet session is established, and network resources to support the packet session are allocated and ‘reserved’ at the target technology network for the multi-mode mobile device until a handover is required. When an inter-technology handover becomes necessary or required, rather than having to complete the initial network entry procedures and packet session establishment at the target technology network at the time of inter-technology handover, the user's services are simply moved from the serving technology node to the pre-configured packet session at a target technology network node resulting in seamless session continuity during inter-technology handover and minimal data loss than otherwise possible.
A dual or multi-mode mobile device includes dual receiver circuitry allowing it to receive signals from two heterogeneous technology nodes at the same time. These mobile devices include dual transmitter circuitry enabling them to transmit to two target nodes or base stations configured to support two different air interface concurrently. They also include mobile devices with single transmitter circuitry in which case the mobile device communicates with the target technology node by ‘piggybacking’ or ‘encapsulating’ air interface signaling destined for the target network within signaling destined to its current serving network node. The serving network then forwards the mobile's air interface signaling to the target technology network via a inter-technology network interface between the serving and target networks.
Given the number of multi-mode devices that may be present at a given time within a target technology network's coverage area, particularly in an ‘overlay’ type network, the resources consumed at the target technology network to complete initial network entry procedures and packet session pre-establishment for potential inter-technology handovers from multi-mode mobile devices at a heterogeneous serving technology network may be significant. This results in degradation and deterioration of network performance in the target technology network since resources that may be allocated to potentially revenue generating mobile devices either active in the target technology network or actually handing over to the network are instead allocated to multi-mode mobile devices receiving service from another serving technology network that may handover to the target technology network at some time in the future or perhaps never at all.
Once initial network entry procedures are completed and a session is pre-established or reserved at the target technology network for an inter-technology handover that may occur in the future, there is no guarantee when the multi-mode mobile device will actually complete an incoming handover to the target technology network unless the handover is initiated by the network, hence the resources associated with maintaining the packet session may be allocated indefinitely. Thus, there is a need to be able to support seamless session continuity during inter-technology handovers while minimizing resource requirements at the target technology network.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.